The present invention relates to scissors, and in particular to folding scissors of a type that can be included in compact multipurpose hand tools.
One type of folding scissors used in compact multipurpose tools such as the model PST II.TM. tool manufactured by Leatherman Tool Group, Inc., the assignee of the present invention, includes a first blade attached to a handle in which the entire scissors can be stored when folded. A second blade is attached to the first blade through a pivot assembly, and a small operating lever for the second blade also moves with respect to both blades, about the axis of the same pivot assembly. In an operating configuration the operating lever of such folding scissors moves the second blade with respect to the first blade. Scissors of this type are disclosed in U.S. Pat. No. 5,745,997.
For use of such scissors in a compact multipurpose tool the operating lever and each of the blades must be large enough to have sufficient strength, yet the scissors should be small enough to be able to be folded and stored within a the handle of the multipurpose tool. For this reason the interconnection between the operating lever and the second blade should not unduly increase the width of the scissors.
At the same time, when the scissors are in use the connection between the operating lever and the second blade must be capable of carrying a reasonable amount of force, so that the scissors can be used to cut materials of a reasonable thickness and toughness.
It is necessary to keep the sharp edges of scissors blades substantially in contact with each other during use. In ordinary scissors excess clearance between the sharp edges of cooperating blades is often reduced by urging the scissors handles apart, so that the sharpened edges are urged together by reaction about the pivot shaft interconnecting the scissors blades. When this same type of force is applied to the operating lever of folding scissors of the type described in the previously-mentioned U.S. Pat. No. 5,745,997, if there is excessive axial clearance along the pivot shaft, the operating lever could be urged laterally out of driving engagement with the second blade. It is possible to reduce this likelihood by constructing the scissors with careful control of the amount of axial clearance in the pivot joint between the scissors blades and the operating lever. The amount of clearance is critical, though, since too little clearance between the blades can make it unduly difficult to move the blades with respect to each other. At the same time, while it should be easy to move the operating lever between its operational position and its folded position, during use of the scissors the operating lever should remain engaged with the adjacent blade.
What is needed, then, is a pair of folding scissors of the general type described above in which the operating lever remains safely and securely engaged with the adjacent blade while a reasonable amount of force is applied to close the scissors blades toward each other in a cutting action, with the sharp edges of the scissors blades held closely enough together to cut efficiently, and yet the scissors should be able to be folded and unfolded easily.